ACTL8 (actin-like protein 8) is a cancer-testis antigen family member with predominantly cytoplasmic localization that functions as an oncogenic driver across multiple cancer types. Primary Function: ACTL8 promotes malignant cell behaviors including proliferation, migration, and invasion 1234. Mechanism: ACTL8 activates multiple pro-growth signaling pathways. In head and neck squamous cell carcinoma and gastric cancer, ACTL8 upregulates the PI3K/AKT pathway 25. In breast cancer, ACTL8 drives glutamine metabolism through MYC-dependent upregulation of metabolic enzymes SLC1A5 and GLS1 while activating PI3K/AKT/mTOR signaling 6. In endometrial and oral cancers, ACTL8 promotes cell cycle progression via CDK1, cyclin E1, cyclin B2, and c-Myc upregulation while suppressing epithelial differentiation markers like E-cadherin 13. Disease Relevance: ACTL8 is significantly upregulated in endometrial cancer, head and neck squamous cell carcinoma, oral squamous cell carcinoma, lung adenocarcinoma, gastric cancer, and breast cancer tissues 123456. Clinical Significance: High ACTL8 expression independently predicts poor prognosis and shorter overall survival across multiple cancer types 123457. ACTL8 represents a promising therapeutic target and prognostic biomarker for cancer treatment.